The form of the county name is unique in England. Many counties are named after their principal town, and the expected form here would be Durhamshire. But County Durham did not become a Shire/County until after the language of government was changed from Anglo-Saxon to Norman French in 1066. Previous to that it was a semi-independent Bishopric.[1] Durham County Council promotes the non-metropolitan county for tourism purposes as "The Land of the Prince Bishops" in reference to the former palatine jurisdiction of the bishops.[2]

In 1889 the administrative county of Durham consisted of the historic county less the county boroughs of Gateshead, South Shields and Sunderland. The boundary with the North Riding of Yorkshire was adjusted: the part of the town of Barnard Castle that was in Yorkshire was added to County Durham, but the part of the Borough of Stockton-on-Tees in Durham was given to the North Riding. For all non-administrative purposes, such as lieutenancy, the County of Durham comprised the administrative county and associated county boroughs.

Over its existence, the administrative county lost territory, both to the existing county boroughs, and also due to the creation of county boroughs at West Hartlepool in 1902 and Darlington in 1915. In 1967 the borough of Hartlepool was removed from the administrative county when it merged with West Hartlepool to form a new county borough of Hartlepool, and in 1968 Billingham was included within the boundaries of the county borough of Teesside, associated with the North Riding.

In 1974 Durham was divided between three counties. The boroughs of Hartlepool and Stockton-on-Tees became a part of the new non-metropolitan county of Cleveland. The metropolitan county of Tyne and Wear became responsible for Gateshead, Sunderland and South Tyneside.[3] The new non-metropolitan county of Durham also covered the former area of Startforth Rural District, a part of the historic North Riding of Yorkshire, and south of the historical boundary of the River Tees.

The Department for Communities and Local Government has said that the seven district councils and the County Council will be abolished and a new unitary authority for the whole of the existing County Council area will be created. The change will be on 1 April 2009 at the latest.[4][5] The successful Durham County Council bid referred to the new authority as County Durham Council.

In 1997 the non-metropolitan county (including unitary Darlington), together with that part of the former county of Cleveland north of the River Tees became a ceremonial county. Lord-lieutenants and high sheriffs are appointed to the ceremonial county of Durham. they have no job in local government.